A flexible Regional Ocean Modeling System-based hybrid coupled model for El Niño–Southern Oscillation studies – model formulation and performance evaluation
Journal
Geoscientific Model Development
Journal Volume
18
Journal Issue
17
Start Page
5527
End Page
5547
ISSN
1991-9603
Date Issued
2025-09-03
Author(s)
Abstract
El Niño–Southern Oscillation (ENSO) constitutes the most prominent interannual climate variation mode in the climate system that originates from ocean–atmosphere interactions in the tropical Pacific. Accurately modeling ENSO variation has consistently posed a great challenge, exhibiting strongly model-dependent representations and simulations of ENSO. This study presents a novel hybrid coupled model (HCM), denoted HCMROMS, built upon the Regional Ocean Modeling System (ROMS) that has been widely used for regional modeling studies. For basin-wide applications to the tropical Pacific, here, the ROMS is coupled with a statistical atmospheric model. The statistical atmospheric model is based on singular value decomposition (SVD), capturing interannual relationships of atmospheric perturbations such as wind stress and freshwater flux anomalies with sea surface temperature (SST) anomalies. The model is constructed in a flexible way so that various components representing atmospheric forcing and oceanic biogeochemistry can be easily included as a module in the HCMROMS. Results demonstrate that the HCMROMS can simulate a stable quasi-3-year ENSO cycle when the interannual wind stress coupling coefficient, ατ, is set to 1.5. The HCMROMS reproduces the three-dimensional (3D) evolution of ENSO-related anomalies, revealing that the most pronounced temperature anomalies occur beneath the surface at 150 m. The interannual temperature anomaly budget highlights the dominance of the advection process in simulated ENSO. Vertical mixing contributes negatively to ENSO anomalies, damping temperature anomalies from the surface due to the turbulent heat flux feedback. This newly developed HCMROMS is poised to serve as an efficient modeling tool for ENSO research in the future.
Subjects
advection
atmospheric forcing
atmospheric modeling
El Nino-Southern Oscillation
heat flux
numerical model
sea surface temperature
singular value decomposition
temperature anomaly
wind stress
Publisher
Copernicus GmbH
Type
journal article